Modern digital cameras for taking pictures of scenes and the like typically include an imaging device which is controlled by a computer running a single threaded process. When an image is captured, the imaging device is exposed to light and generates raw image data representing the image. The raw image data is typically stored in a single image buffer where it is then processed and compressed by the processor. Many types of compression schemes are used to compress the image data, with the joint photographic expert group (JPEG) standard being the most popular. After the processor processes and compresses the raw image data into JPEG image files, the processor stores the JPEG image files into an internal memory or on an external memory card.
Some digital cameras are also equipped with a liquid-crystal display (LCD) or other type of display screen on the back of the camera. Through the use of the LCD, the processor can cause the digital camera to operate in one of two modes, record and play, although some cameras only have a record mode. In record mode, the LCD is used as a viewfinder in which the user may view an object or scene before taking a picture. In play mode, the LCD is used a playback screen for allowing the user to review previously captured images either individually or in arrays of four, nine, or sixteen images.
Besides the LCD, digital camera user interfaces also include a number of buttons or switches for setting the camera into one of the two modes and for navigating between images in play mode. For example, most digital cameras include two buttons labeled "-" and "+" that enable a user to navigate or scroll through captured images. For example, if the user is reviewing images individually, meaning that single images are displayed full-sized in the LCD, pressing one of navigation buttons causes the currently displayed image to be replaced by the next image.
To display a captured image in play mode, the processor must first access the JPEG image file corresponding to the captured image from memory, decompress the image data sixteen horizontal lines at time, and then send the decompressed data to the LCD. When the user presses the navigation button to see the next image, the user sees the next image slowly replace the previously displayed image from top to bottom. Due to the amount of processing involved, the display of the entire image may take several seconds in some cameras. Not only is the image decompression time slow, but conventional digital cameras also do not allow other camera operations while the JPEG image is being decompressed, which means that the user cannot abort the decompression process. Thus, if the user decides halfway through reviewing a current image that another image is preferred, the camera will not recognize the next action until the current image is fully displayed.
Accordingly, a user interface of this type appears to the user as being slow and non-responsive when attempting to access multiple images on a digital camera. Speed of access to these images has become increasingly important as these types of cameras have become more widely available.
There is a need, therefore, to provide images on a display device which allows the user to review multiple captured images, while simultaneously providing a display and a readout for a particular image in an efficient and straightforward manner. It is similarly important to be able to rapidly identify a recognizable representation of the image. Finally, the system and method should be more responsive to the user than previously known systems. For example, in a plurality of captured images, it would be useful to quickly identify two or more particular images quickly, with a minimum of effort. It is also important to provide more efficient ways to quickly navigate through a series of images. The system should be implementable in a simple and cost effective fashion and should be easily handled by a user. The present invention addresses such a need.